A thermal insulation pipe, such as a water-supply pipe, is generally known from the technology disclosed by Japanese Patent Laid-open (Unexamined) Publication No. 2000-81192. This has the construction wherein a vacuum layer is formed in an interspace of a double tube 60 comprising an inner tube 61 and an outer tube 62, as shown in FIG. 2. The space between the inner and outer tubes is provided with a hollow fiber membrane unit 70 and minute hollow glass beads 80. The hollow fiber membrane unit 70 suppresses collision of gas molecules in that space. The minute hollow glass beads 80 provide increase of heat transfer distance. The combination of the hollow fiber membrane unit 70 and the minute hollow glass beads 80 provides enhanced thermal insulation effects. The interspace is provided, at an end thereof, with a sealing portion 85 formed by casting epoxy resin or equivalent. This thermal insulation tube including the vacuum layer must be provided with an evacuation port 90 to be connected with a vacuum evacuation device, for evacuation of the thermal insulation pipe. In general, the evacuation port 90 is oriented orthogonal to the thermal insulation pipe and is projected radially therefrom.
However, when the evacuation port is oriented orthogonal to the thermal insulation pipe, a maximum width D2 of the thermal insulation pipe at the evacuation port becomes larger than a maximum outer diameter D1 of the thermal insulation pipe (D2>D1). As a result of this, when the thermal insulation pipe is set, for example, in a pipeline or a narrow space, the evacuation port itself becomes an obstacle as a projecting part and thus imposes restrictions on the space where the thermal insulation pipe may be set in.
Further, when this thermal insulation pipe is set in, the projecting evacuation port, or a tip portion of the evacuation port to be connected with the vacuum evacuation device, in particular, is vulnerable to damage. Due to this, when the thermal insulation pipe having the projecting evacuation port is inserted in a pipeline or equivalent, some protection must be given to the evacuation port.
It is a principal object of the invention to provide a thermal insulation piping that provides no projecting part around an outside thereof to facilitate insertion of the thermal insulation piping in a pipeline.